Color correction is a process used in many color applications. In a particularly useful application, color correction is employed in film post-production workflow. One purpose for color correction is to alter the color, brightness, contrast, color temperature, etc. of an image or part of the image so as to change the “look” of an image. Traditional color correction is purely a two-dimensional (2D) technique which does not allow users to take into account or modify the conditions involved in the image formation process, such as light source position, surface material and surface geometry, to name a few.
Color correction is an important process implemented in a film post-production workflow. Color correction processes are conducted by colorists with the aid of software systems, such as, for example, Da Vinci™ (now owned by JDS Uniphase™ Inc.), Lustre™ (now owned by Discreet, Autodesk™ Inc.), and others. The color correction functionality implemented by these systems includes region selection, color grading, defocus, key channel and matting, Gamma control, brightness, contrast, etc. Some special effects such as shadowing and shading of surfaces may be realized using such software packages by using solely two-dimensional (2D) procedures (for example, using matte and key channel). However, currently no three-dimensional (3D) information and image formation theory has been employed by such software packages for facilitating color correction.
Compositing is a related technique which is also an important process in film post-production. Compositing combines images from multiple sources, including computer generated elements. A typical example of compositing is the blue-screen technique in which a blue key color in a movie frame is replaced by a background plane to achieve special visual effects. The traditional blue-screen technique is a 2D procedure in the sense that the 3D geometry and lighting conditions of the scene are not taken into account. Consequently, the lighting environment of foreground and background planes may not be compatible in a final composite image frame. As such, an additional color correction process has to be performed after the compositing process using software, for example, to correct for the incompatible lighting conditions.
Although color correction is extensively used in various applications, such as film post-production, the current color correction processes and software applications do not enable users to manipulate and/or account for 3D properties of an image capture process such as the three-dimensional geometry of a scene, light source conditions and positions and surface reflectance properties. As such, applications in which such factors have to be considered are limited and require additional post-processing.